People with a gene linked to long life and good health are also less likely to develop Alzheimer's disease, U.S. researchers said on Tuesday.

They said people with two copies of a certain version of the cholesteryl ester transfer protein or CETP gene had significantly slower memory declines compared with people who had different versions of the gene.

"We've known for a long time that genetic factors matter in Alzheimer's disease," said Dr. Richard Lipton of Albert Einstein College of Medicine at Yeshiva University in New York, whose study appears in the Journal of the American Medical Association.

Lipton said most studies have sought to identify genetic variations that increase the risk of developing Alzheimer's disease, such as APOE4.

"Instead, we looked at genes that protect Alzheimer's disease, and also for genes that might promote healthy brain aging," Lipton said in a telephone interview.